This invention relates to catalyst systems useful for polymerizing alpha-olefins and particularly relates to a supported titanium halide catalyst component and a catalyst system containing such component and more particularly to a dry solid catalyst component.
Magnesium-containing supported titanium halide-based alpha-olefin polymerization catalyst components are now well known in the art. Typically, these catalysts are recognized for their performance based on activity and stereospecificity. However, commercial olefin polymerization, especially gas-phase alpha-olefin polymerization, requires additional catalyst attributes for economical large-scale operation.
One such attribute is the ability to store and transport catalyst components without significant amounts of volatile hydrocarbon contents. As prepared, such titanium halide based components contain significant amounts of volatile hydrocarbons from either reactant diluents or wash liquids. Since transporting materials containing volatile hydrocarbons such as hexane pose a safety concern, it is advantageous to reduce the amounts of these volatile compounds. Another incentive to produce a relatively dry catalyst component is adding measured amounts of catalyst component to a reactor, since the amount of volatile hydrocarbons may vary. However, in U.S. Pat. No. 4,290,915 previous magnesium-titanium-halide supported catalysts have been found to require more than 1 wt. % hydrocarbon for optimum performance.
The present invention incorporates a series of catalyst formation process steps described in U.S. Pat. No. 4,866,022 which produce a catalyst with exceptionally high activity and stereospecificity combined with very good morphology and which may be dried to less than 1 wt. % volatile hydrocarbon and maintain catalyst performance.